Low Water Biomass-Derived Pyrolysis Oils and Processes for Producing the Same

ABSTRACT

Low water-containing biomass-derived pyrolysis oils and processes for producing them are provided. The process ( 200 ) includes condensing ( 204 ) pyrolysis gases including condensable pyrolysis gases and non-condensable gases to separate the condensable pyrolysis gases from the non-condensable gases, the non-condensable gases having a water content, drying ( 206 ) the non-condensable pyrolysis gases to reduce the water content of the-non-condensable gases to form reduced-water non-condensable pyrolysis gases, and providing ( 208 ) the reduced-water non-condensable pyrolysis gases to a pyrolysis reactor for forming the biomass-derived pyrolysis oil.

STATEMENT OF PRIORITY

This application claims priority to U.S. application Ser. No. 12/842,394which was filed on Jul. 23, 2010.

FIELD OF THE INVENTION

The present invention generally relates to biofuels, and moreparticularly relates to low water biomass-derived pyrolysis oils andprocesses for producing the same.

DESCRIPTION OF RELATED ART

Biomass-derived pyrolysis oil may be employed as fuel for a variety ofapplications. For example, biomass-derived pyrolysis oil can serve asfuel for certain boiler and furnace applications. In other instances,the biomass-derived pyrolysis oil can be provided as a potentialfeedstock in catalytic processes for the production of fuel in petroleumrefineries. Recently, the use of biomass-derived pyrolysis oil as atransportation fuel has been investigated, which could reduce consumerdependency on conventional petroleum and reduce environmental impact.

To form biomass-derived pyrolysis oil, processes such as rapid pyrolysisare commonly used. Generally during rapid pyrolysis, organic biomassmaterials, such as wood waste, agricultural waste, etc., are rapidlyheated in a process reactor in the absence of air to temperatures in arange of 450° C. to 600° C. to yield organic vapors, water vapor,pyrolysis gases, and ash (char). The organic and water vapors arecondensed to form biomass-derived pyrolysis oil.

Although conventional pyrolysis processes produce useful forms of thebiomass-derived pyrolysis oil, the processes may be improved. Forexample, though the biomass is typically subjected to drying to removemore than 90% of its water content prior to being provided to thepyrolysis reactor, conventionally-produced biomass-derived pyrolysisoils still may yield complex, highly oxygenated organic liquidscontaining 20-30% by weight of water. The high water content of theconventionally-produced biomass-derived pyrolysis oil can, over time,cause phase separation, and can reduce the energy density of thepyrolysis oil. Additionally, drying the biomass before pyrolysisconsumes large amounts of energy.

Accordingly, it is desirable to provide processes for producing lowwater biomass-derived pyrolysis oil that may be performed by consumingless energy than conventional pyrolysis processes. Additionally, it isdesirable to produce low water biomass-derived pyrolysis oil havingsubstantially increased storage stability. Furthermore, other desirablefeatures and characteristics of the present invention will becomeapparent from the subsequent detailed description of the invention andthe appended claims, taken in conjunction with the accompanying drawingsand this background of the invention.

SUMMARY OF THE INVENTION

In an embodiment, a process for reducing water in a biomass-derivedpyrolysis oil includes condensing pyrolysis gases comprising condensablepyrolysis gases and non-condensable gases to separate the condensablepyrolysis gases from the non-condensable gases, the non-condensablegases having a water content, drying the non-condensable pyrolysis gasesto reduce the water content of the-non-condensable gases to formreduced-water non-condensable pyrolysis gases, and providing thereduced-water non-condensable pyrolysis gases to a pyrolysis reactor forforming the biomass-derived pyrolysis oil.

In another embodiment, a process for preparing a low waterbiomass-derived pyrolysis oil includes introducing pyrolysis gases intoa condenser, the pyrolysis gases comprising condensable pyrolysis gasesand non-condensable pyrolysis gases, the non-condensable gases having awater content. The condenser is adjusted to a predetermined temperatureto provide a threshold vapor pressure of water in the condenser tothereby provide a maximum water content for retention in thebiomass-derived pyrolysis oil. Pyrolysis gases are condensed in thecondenser to separate the condensable pyrolysis gases from thenon-condensable gases. The non-condensable pyrolysis gases are dried toreduce the water content of non-condensable pyrolysis gases to formreduced-water non-condensable pyrolysis gases. The reduced-waternon-condensable pyrolysis gases are provided to a pyrolysis reactor forforming the biomass-derived pyrolysis oil.

In still another embodiment, a process for preparing a low waterbiomass-derived pyrolysis oil includes condensing pyrolysis gasescomprising condensable pyrolysis gases and non-condensable gases toseparate the condensable pyrolysis gases from the non-condensable gases,the non-condensable gases having a water content. The non-condensablepyrolysis gases are dried to reduce the water content ofthe-non-condensable gases to form reduced-water non-condensablepyrolysis gases. The reduced-water non-condensable pyrolysis gases areprovided to a pyrolysis reactor for forming the biomass-derivedpyrolysis oil. A biomass material is pyrolyzed in the pyrolysis reactorwith the reduced-water non-condensable pyrolysis gases to formreduced-water pyrolysis gases. The reduced-water pyrolysis gases arecondensed to form the low water biomass-derived pyrolysis oil, the lowwater biomass-derived pyrolysis oil having a water content in a range of2% to 30%.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will hereinafter be described in conjunction withthe following drawing figures, wherein like numerals denote likeelements, and wherein:

FIG. 1 is a simplified schematic of a system for producing low waterbiomass-derived pyrolysis oil, according to an embodiment; and

FIG. 2 is a flow diagram of a process for reducing the water content ofbiomass-derived pyrolysis oil to produce low water biomass-derivedpyrolysis oils, according to an embodiment.

DETAILED DESCRIPTION

The following detailed description of the invention is merely exemplaryin nature and is not intended to limit the invention or the applicationand uses of the invention. Furthermore, there is no intention to bebound by any theory presented in the preceding background of theinvention or the following detailed description of the invention.

An improved biomass-derived pyrolysis oil and processes for producingthe improved biomass-derived pyrolysis oil are provided. The improvedbiomass-derived pyrolysis oil has a water content that is less than thatof conventionally-produced biomass-derived pyrolysis oils. In accordancewith an embodiment, the improved biomass-derived pyrolysis oil has awater content in a range of 2% to 30%. In another embodiment, the watercontent of the improved biomass-derived pyrolysis oil is lower than theaforementioned range.

FIG. 1 is a simplified schematic of a system 100 that may be employedfor producing low water biomass-derived pyrolysis oil, in accordancewith an embodiment. Although not depicted, the system 100 may include anumber of additional or alternative components, such as blowers, pumps,storage tanks or other devices for use in forming a biomass-derivedpyrolysis oil. Moreover, the components described in system 100 need notbe placed in the illustrated order, and the system 100 may beincorporated into a more comprehensive system having additionalfunctionality not described in detail herein. Furthermore, one or moreof the components of system 100 may be omitted from an embodiment of thesystem 100 as long as the intended overall functionality of the system100 (e.g., to form biomass-derived pyrolysis oil) remains intact.

Generally, the system 100 includes a feed bin 102, a pyrolysis reactor104, a reheater 106, a condenser 108, and a dryer 110. The components ofsystem 100 are in flow communication via conduits, tubes or other linesthrough which gas, liquids, and/or solids can flow.

The feed bin 102 is configured to receive biomass material from a feedsource (not shown). The biomass material comprises a carbonaceousbiomass feedstock, and includes, but is not limited to wood,agricultural wastes/residues, nuts and seeds, algae, grasses, forestryresidues, municipal solid waste, construction and/or demolition debris,cellulose and lignin or the like. In accordance with an embodiment, thefeed bin 102 provides the biomass material to a feed conveyor 112 incommunication with the pyrolysis reactor 104. The feed conveyor 112conveys the biomass material into the pyrolysis reactor 104.

The pyrolysis reactor 104 pyrolyzes the biomass material to producechar, vapor, and pyrolysis gases. In this regard, the pyrolysis reactor104 comprises any one of numerous types of pyrolysis reactors suitablefor pyrolyzing biomass material. Examples of suitable pyrolysis reactorsinclude, but are not limited to fixed bed pyrolysis reactors, fluidizedbed pyrolysis reactors, circulating fluidized bed reactors (CFBR), orother pyrolysis reactors capable of pyrolysis. Other pyrolysis reactorscan be used in other embodiments.

The pyrolysis reactor 104 generally includes a reactor riser 114 withinwhich a heat transfer medium (not shown) is disposed. The reactor riser114 is generally tubular. In another embodiment, the reactor riser 114is a box or has another shape suitable for housing the heat transfermedium. The heat transfer medium includes inert solids suitable fordirectly or indirectly transferring heat to the biomass material withinthe reactor riser 114, such as sand, catalytic materials, or acombination thereof. The heat transfer medium may be provided in afluidized state and maintained at a temperature suitable for pyrolysisto pyrolyze the biomass material.

A first separator system 120 is in flow communication with the pyrolysisreactor 104 and is configured to separate solids from gases. Forexample, the first separator system 120 receives pyrolyzed materialsfrom the pyrolysis reactor 104 and separates solids making up the heattransfer medium from pyrolysis gases included in the pyrolyzedmaterials. Suitable devices for inclusion in the separator system 120include, but are not limited to, cyclonic recirculation apparatus, andthe like. A line 122 provides communication between the first separatorsystem 120 and the reheater 106, which reheats the heat transfer mediacollected from the first separator system 120. A conduit 128 provides apathway from the reheater 106 to the pyrolysis reactor 104 to allow thereheated heat transfer media to return to the pyrolysis reactor 104 foruse.

A second separator system 124 captures solids and gases exiting from thereheater 106. The second separator system 124 can include a cyclonicrecirculation apparatus or the like. The solids from the reheater 106,which may comprise by-product ash, are collected and removed from thesystem 100 via a conduit 132. Gases exiting the separator system 124 areexhausted from the system 100 through conduit 134.

The condenser 108 is disposed in communication with the pyrolysisreactor 104 and receives the pyrolysis gases from the pyrolysis reactor104. The condenser 108 is configured to cool condensable gases causingthe condensable gases to phase change into liquid. For example, thepyrolysis gases comprise a condensable portion (also referred to as“condensable pyrolysis gases”) and a non-condensable portion (alsoreferred to as “non-condensable pyrolysis gases”), and the condenser 108cools the condensable portion of the pyrolysis gases to transform aportion of the condensable pyrolysis gases into liquid. The condenser108 may also be configured to be adjusted to a predetermined temperatureto provide a threshold vapor pressure of water in the condenser 108,such that a predetermined maximum pyrolysis water content is retained bythe resulting biomass-derived pyrolysis oil. Accordingly, thenon-condensable pyrolysis gases have a vaporous water content that isdependent on a vapor pressure of water in the condenser. Althoughdepicted as being a single condenser 108 in FIG. 1, the condenser 108can include more than one unit placed in series, in other embodiments.Suitable types of condenser include, but are not limited to surfacecondensers, such as heat exchange-type condensers, liquid quenchcondensers and the like. In other embodiments, another type of condensermay be employed.

Liquid collected by the condenser 108 is carried away via a conduit 136.A portion of the liquid flows through another conduit 138 to a cooler126, while another portion of the liquid is diverted through conduit 142and removed from the system 100 as the biomass-derived pyrolysis oil. Inan example, the biomass-derived pyrolysis oil is directed to a storagetank (not shown). The cooler 126 cools the received portion of theliquid from the condenser 108 and redirects the liquid to the condenser108 to be used as a coolant for the condenser 108.

Non-condensable pyrolysis gases not condensed by the condenser 108 flowfrom the condenser 108 into a conduit 140 to be re-used in the system100. The non-condensable pyrolysis gases, which include hydrogen gas,methane, and carbon oxides, can be used to provide combustion energyfuel for use in various components of the system 100 or elsewhere. In anexample, a portion of the non-condensable pyrolysis gases is re-directedfrom conduit 140 to a dryer (not shown) to dry the biomass materialprior to being fed to the feed bin 102. For instance, the redirectedportion of the non-condensable pyrolysis gases is diverted into conduit150 at junction 146 and flows toward the dryer. In another example, aportion of the non-condensable pyrolysis gases is diverted from conduit140 into conduit 148 and delivered to the reheater 106 to be burnt.Still another portion of the non-condensable pyrolysis gases is providedto the pyrolysis reactor 104 to serve as fluidizing gas in the pyrolysisreactor to mix the heat transfer medium in the reactor riser 114 (e.g.,sand) with the biomass. Accordingly, the non-condensable pyrolysis gasescontinue along conduit 140 toward the reactor 104.

Prior to introduction into the pyrolysis reactor 104, thenon-condensable pyrolysis gases are de-hydrated to remove water, becausewater can reduce the quality of the pyrolysis oils formed by pyrolysis.In this regard, the dryer 110 is disposed between the condenser 108 andthe pyrolysis reactor 104. As used herein, the term “dryer” is definedas an apparatus capable of removing water from a gas or liquid. In anembodiment, the dryer 110 is selected for being capable of removing atleast 50% of the water content of the non-condensable pyrolysis gases.In another embodiment, the dryer 110 is selected for being capable ofremoving at least 90% of the water content of the non-condensablepyrolysis gases. In still another embodiment, the dryer 110 removes lessthan 50% of the water content of the non-condensable pyrolysis gases.

A variety of different apparatus configured to remove the water can beemployed for removing water from the non-condensable pyrolysis gases.For example, the dryer 110 can be configured to remove the water bycooling the non-condensable pyrolysis gases to a predeterminedtemperature at which the water liquefies, and the water is collected anddiverted to a collection tank 130. In such an embodiment, the dryer 110comprises a chiller. In another embodiment, the dryer 110 can beconfigured to remove molecules of water as the non-condensable gasesincluding the water passes through the dryer 110. In such aconfiguration, an adsorptive drier, such as a molecular sieve can beused as the dryer 110. In an example, the molecular sieve is selected toentrap molecules in a size range of 3 Angstroms to 5 Angstroms. Inanother embodiment, the adsorptive dryer can include a pillared clay,alumina, salt or another type of molecular sieve. The water removed fromthe dryer 110 flows along conduit 152 out of the system 100, in anembodiment. In another embodiment, the conduit 152 is in flowcommunication with a storage tank or reservoir (not shown).

According to another embodiment, the system 100 further includes a gaspre-treatment zone 144 to prepare the reduced-water non-condensablepyrolysis gases for introduction into the dryer 110. FIG. 2 is a flowdiagram of a process 200 for forming a low water biomass-derivedpyrolysis oil, according to an embodiment. Process 200 represents oneimplementation of a method for forming the low water biomass-derivedpyrolysis oil. For illustrative purposes, the following description ofprocess 200 may refer to components mentioned above in connection withFIG. 1. In practice, portions of process 200 may be performed bydifferent components of the described system 100, e.g., the pyrolysisreactor 104, the condenser 108, the dryer 110, etc. Additionally,process 200 may include any number of additional or alternative steps,the steps shown in FIG. 2 need not be performed in the illustratedorder, and process 200 may be incorporated into a more comprehensiveprocedure or process producing additional products not described indetail herein. Moreover, one or more of the steps shown in FIG. 2 couldbe omitted from an embodiment of the process 200 as long as the overallintention, e.g., to produce a low water biomass-derived pyrolysis oil,remains intact.

Process 200 begins with pyrolyzing a biomass material to obtainpyrolysis gases, step 202. The biomass material comprises one or more ofthe biomass materials mentioned previously in connection with feed bin102, in an embodiment. In another embodiment, the biomass material isanother carbonaceous biomass material. The biomass material can beprepared prior to being pyrolyzed. For example, in some cases, thebiomass material includes water, and water is removed from the biomassmaterial. The biomass material may be dried such that a water content ina range of 4% to 20% remains. In another embodiment, the biomassmaterial is comminuted to a particle size of 0.5 mm to 12 mm. Thebiomass material is then fed to a pyrolysis reactor (e.g., reactor 104)and pyrolyzed.

Pyrolysis includes rapidly heating the biomass material in the pyrolysisreactor at a rate of 500° C. per second to 50,000° C. per second in theabsence of air. In other embodiments, the pyrolysis processes may beperformed using processing parameters that are different than thosepreviously mentioned. Although the aforementioned rapid pyrolysisprocess is described, other embodiments can employ other pyrolysisprocesses. For example, other types of pyrolysis processes suitable forobtaining pyrolysis gases include, but are not limited to vacuumpyrolysis, catalytic pyrolysis, and slow pyrolysis (also known ascarbonization).

After the biomass feedstock has been pyrolyzed, solid char, vapors, andpyrolysis gases are formed. The solid and gas products (e.g., solidchar, vapors, and pyrolysis gases) and, in some cases, a portion of aheat transfer medium from the pyrolysis reactor, exit the pyrolysisreactor. To isolate the gas products (e.g., vapors and pyrolysis gases)from the solid char and heat transfer media, the gas products, solidchar, and heat transfer media are directed into a separator system(e.g., system 120). The solid char and heat transfer media areredirected to a heater (e.g., heater 106) for char combustion andreheating of the heat transfer media. For example, the heat transfermedium may be reheated by oxidation at temperatures in a range of 400°C. to 750° C. at slightly above ambient pressure. The heat transfermedia circulation rate may be used to control the temperature of acombustion bed in the heater. Alternatively, diluted air may be used tocontrol the rate of combustion within the reheater. The regenerated heattransfer medium and solid char may be directed to another separatorsystem to remove the solid char from the regenerated heat transfermedium. Then, the regenerated heat transfer medium may be recycled tothe pyrolysis reactor.

The pyrolysis gases are condensed to separate the condensable pyrolysisgases from the non-condensable pyrolysis gases, step 204. The pyrolysisgases are introduced into and flow through the condenser or series ofcondensers to cool the condensable pyrolysis gases and to cause thecondensable pyrolysis gases to phase change into liquid, while thenon-condensable pyrolysis gases remain in gaseous phase. In anembodiment, the condenser cools the pyrolysis gases to a temperature ina range of 10° C. to 90° C. suitable for causing the condensablepyrolysis gases to phase change to liquid. In accordance with anembodiment, the temperature in the condenser 108 is adjusted to a higheror lower temperature to thereby control a vaporous water content of thenon-condensable pyrolysis gases. For example, a temperature above 60° C.allows an amount of water that remains with the non-condensablepyrolysis gases to be lower than the amount retained in thenon-condensable pyrolysis gases if the temperature of the condenser 108was adjusted to a lower temperature. As alluded to above, thecondensable pyrolysis gases condense into the biomass-derived pyrolysisoil, which can be diverted to a storage tank (not shown) or may bedirected to a cooler (e.g., cooler 124) for use in the condenser duringsubsequent condensing processes. The non-condensable pyrolysis gasescomprising hydrogen gas, methane, carbon oxides, and water, flows out ofthe condenser toward the reactor.

Prior to flowing back to the reactor, the non-condensable pyrolysisgases are dried to reduce a water content of the non-condensablepyrolysis gases and to form reduced-water non-condensable pyrolysisgases, step 206. In an embodiment, the non-condensable pyrolysis gasesare subjected to a temperature in a range in which a portion of thewater vapor changes phase to liquid, while the non-condensable pyrolysisgases remain in gaseous phase. Suitable temperatures include, but arenot limited to 0° C. to 90° C. In another embodiment, the water in thenon-condensable pyrolysis gases is adsorbed using an adsorptive dryer.Regardless of the particular drying process, the water content of thenon-condensable pyrolysis gases preferably is reduced by at least 50%.In another embodiment, the water content of the non-condensablepyrolysis gases is reduced by at least 90%. In other embodiments, thewater content is reduced by less than 50%. In any case, removing waterfrom the non-condensable pyrolysis gases produces the reduced-waternon-condensable pyrolysis gases, which are provided to the pyrolysisreactor for forming a low water biomass-derived pyrolysis oil, step 208.

In some embodiments of process 200, the reduced-water non-condensablepyrolysis gases are subjected to pre-treatment steps prior tointroduction into the dryer, step 208. For instance, the reduced waternon-condensable pyrolysis gases are heated in order to prevent liquidsfrom condensing on adsorptive media disposed within the dryer. In anembodiment, suitable heating temperatures include those in a range of 5°C. to 150° C. above the temperature employed in step 206. In otherembodiments, the reduced water non-condensable pyrolysis gases areheated to higher or lower temperatures than those in the aforementionedrange. In another example, the non-condensable pyrolysis gases arefiltered to reduce a mist load of the gases

To form the low water biomass-derived pyrolysis oil, biomass material ispyrolyzed with the reduced-water non-condensable pyrolysis gases and theprocess reiterates at step 204 and continues at least through step 210.For example, after the biomass material and reduced-waternon-condensable pyrolysis gases are pyrolyzed, reduced-water pyrolysisgases are produced. Specifically, the reduced-water pyrolysis gasesinclude a water content that is lower than the water content ofpyrolysis gases produced by pyrolysis without use of the reduced-waternon-condensable pyrolysis gases. When the reduced-water pyrolysis gasesare condensed, condensable and non-condensable pyrolysis gases areseparated from each other. In particular, the condensable pyrolysisgases condense to form the low water biomass-derived pyrolysis oil.

Hence, by removing water from the non-condensable pyrolysis gases beforethey are employed in the pyrolysis reactor for pyrolysis, the resultingbiomass-derived pyrolysis oil has lower water content than abiomass-derived pyrolysis oil formed without the use of thereduced-water non-condensable pyrolysis gases. Specifically, thebiomass-derived pyrolysis oil formed by process 200 has a water contentin a range of 20% to 30%. In embodiments in which a dried biomassmaterial is pyrolyzed with the reduced-water non-condensable pyrolysisgases, the low water biomass-derived pyrolysis oil may have a watercontent in a range of 2% to 30%. The low water biomass-derived pyrolysisoil is a single phase liquid which exhibits improved storage stabilityand higher energy density over pyrolysis oils formed using conventionalpyrolysis processes. The low water biomass-derived pyrolysis oil is thusmore suitable for use as a biofuel than the starting biomass-derivedpyrolysis oil.

While at least one exemplary embodiment has been presented in theforegoing detailed description of the invention, it should beappreciated that a vast number of variations exist. It should also beappreciated that the exemplary embodiment or exemplary embodiments areonly examples, and are not intended to limit the scope, applicability,or configuration of the invention in any way. Rather, the foregoingdetailed description will provide those skilled in the art with aconvenient road map for implementing an exemplary embodiment of theinvention, it being understood that various changes may be made in thefunction and arrangement of elements described in an exemplaryembodiment without departing from the scope of the invention as setforth in the appended claims and their legal equivalents.

What is claimed is:
 1. A process (200) for reducing water in abiomass-derived pyrolysis oil comprising the steps of: condensing (204)pyrolysis gases comprising condensable pyrolysis gases andnon-condensable gases to separate the condensable pyrolysis gases fromthe non-condensable gases, the non-condensable gases having a watercontent; drying (206) the non-condensable pyrolysis gases to reduce thewater content of the-non-condensable gases to form reduced-waternon-condensable pyrolysis gases; and providing (208) the reduced-waternon-condensable pyrolysis gases to a pyrolysis reactor for forming thebiomass-derived pyrolysis oil.
 2. The process (200) of claim 1, furthercomprising: pyrolyzing (202) a biomass material in the pyrolysis reactorwith the reduced-water non-condensable pyrolysis gases to formreduced-water pyrolysis gases; and condensing (204) the reduced-waterpyrolysis gases to form a low water biomass-derived pyrolysis oil. 3.The process (200) of claim 1, wherein the step of drying (206) comprisespassing the non-condensable pyrolysis gases over a chiller.
 4. Theprocess (200) of claim 1, wherein the step of drying (206) comprisespassing the non-condensable pyrolysis gases through an adsorptive dryer.5. The process (200) of claim 1, wherein the step of passing thenon-condensable pyrolysis gases through an adsorptive dryer comprisespassing the non-condensable pyrolysis gases through a molecular sieve.6. The process (200) of claim 1, wherein the step of condensing (204)pyrolysis gases further comprises introducing the pyrolysis gases into acondenser and adjusting the condenser to a predetermined temperature toprovide a threshold vapor pressure of water in the condenser to providea predetermined maximum water content included in the low waterbiomass-derived pyrolysis oil.
 7. The process (200) of claim 1, furthercomprising the step of heating the reduced-water non-condensablepyrolysis gases, between the steps of condensing and drying.
 8. Theprocess (200) of claim 1, further comprising the step of filtering thenon-condensable pyrolysis gas to reduce a mist load of thenon-condensable pyrolysis gas, between the steps of condensing anddrying.